<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <!-- 要向构造一个json格式的请求，就不需要再使用form了，可以使用ajax -->
        <input type="text" id="userId">
        <input type="text" id="classId">
        <input type="button" value="提交" id="submit">
    
<!-- 想用ajax需要引入jquery -->
<script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<script>
        // $.ajax({
        //     type:'post',
        //     url:'method',
        //     success:function(body){
        //         console.log(body);
        //     }
        // });
        let userIdInput=document.querySelector('#userId');
        let classIdInput=document.querySelector('#classId');
        let button=document.querySelector('#submit');
        button.onclick=function(){
            $.ajax({
                type:'post',
                url:'postJson',
                contentType:'application/json',
                data:JSON.stringify({
                userId:userIdInput.value,
                classId:classIdInput.value
            }),
                
            success: function(body){
                console.log(body);
            }
        });
        }
    </script>
</body>
</html>